Welcome to the Anthropocene, Our New Biogeophysical Home

Mankind’s impact on Earth extends well beyond climate change to the broader biosphere, where the conditions that nurtured the development of modern humans are at risk of being lost in a new epoch known as the Anthropocene.

Climate change makes headline news, but mankind’s changes to planet Earth go well beyond rising temperatures. In this episode of Energy Policy Now prominent earth system scientist Will Steffen explores the dawn of a new geologic epoch, the Anthropocene, where the systems of sea, land, and air will be unlike those experienced in human history.

The term Anthropocene, coined less than two decades ago, emphasizes the rising influence of humans on earth system processes, and our emerging role as the dominant force shaping Earth’s biologic and geologic systems. Steffen looks at the political and economic systems that have accelerated man’s impact on Earth since the middle of the 20th century, and at the role of technology and policy in slowing global change.

Andy Stone: Hi, I’m Andy Stone with the Energy Policy Now podcast from the Kleinman Center for Energy Policy at the University of Pennsylvania. Over the past few months this podcast has looked at the issue of climate change from a number of angles. In our last episode, we examined the risk that climate change poses for investors and how strong climate policies might fundamentally reorient economies. We’ve also looked at the latest research into the expected environmental impacts of a warming climate, and how the issue of climate is debated in the media.

Today, we’ll be talking about how mankind’s impact goes beyond climate to in fact alter the very course of Earth’s geologic history and bring us into a new geologic age. The name for this new time is the Anthropocene. In it, the influence of man overrides Earth’s own biologic and geologic systems, creating a planet that will be very likely different from that in which mankind and society developed.

Today’s guest is Will Steffen, a prominent Earth system scientist and emeritus professor at the Australian National University. Will is the former executive director of the International Geosphere Biosphere Program in Stockholm, Sweden, and a former member of the Australian Government’s Climate Commission. Much of Will’s work has focused on the implications of the Anthropocene shift, which he’ll share with us today. Will, welcome to the podcast.

Will Steffen: Thanks, Andy.

Stone: So, you’ve been working in Earth System Science for many years. Can you tell us what the discipline is and how the concept of Anthropocene developed?

Steffen: Well, the interesting thing about Earth system science is, in fact, it’s not a discipline of its own. It relies on many other disciplines. So it’s a highly integrated area of research, looking at the earth as a single integrated system, so it relies on people from meteorology, from biology, from oceanography, indeed, people from the social economic sphere as well, because humans are an important part of the Earth’s system. So it’s a highly integrative area of research that I think defies the name of the discipline.

So it’s, it’s something that’s probably only been developed in the form we know it today over the last 25 years ago. And of course, is intimately connected with the concept of the Anthropocene. That concept actually arose in the year 2000. At a meeting of the IGBP, the International Geosphere Biosphere Program, when one of our most senior scientists, the Vice Chair, named Paul Crutzen, he’s an actually a Nobel laureate, one of the chemists who understood what was going on with the ozone hole. When he was looking at all the evidence of how the earth has been changing over the past decades and centuries or so. He just sort of blurted out the fact you know, we’ve left the Holocene, all of this stuff you guys are presenting, this isn’t the Holocene anymore. We’re in a new epoch. And he sort of stumbled around a bit and then came up with the word Anthropocene. And so the word in the concept has stuck and developed ever since it was first used in the year 2000.

Stone: So the concept itself goes beyond changing climate patterns and their immediate impacts. It is in fact about a fundamental change of the biosphere in which we live. What specifically defines this new era?

Steffen: Well, first of all, if you consider the earth system, and it’s probably most simple, most simple decomposition of that into a geosphere and a biosphere they are highly interactive. The geosphere being nonliving parts of your system and the biosphere, of course, being life on Earth. And to have co-evolved. But the important point here is that this system, this interactive geosphere biosphere system, can exist in well defined states, with transitions between these states.

And certainly in the last about 3 million years or so, we’ve seen a very systematic, very periodic oscillation between ice ages and warm periods. And the most recent warm period has been named by the geologist as the as the Holocene. So that’s a well defined state of the Earth system, but it’s held in a well defined state by the interactive processes of the geosphere and the biosphere.

So that really is how we define states or conditions of the Earth system. What are the defining characteristics? Well, it’s the suite of life in the biosphere. In other words, you have a stable biosphere, you’re not having a lot of creatures going extinct, or a lot of changes in biomes and so on. And of course, the climate is a good indicator for the geosphere. Temperature sits within a certain well controlled range, you have reasonably stable patterns for the water cycle, the ice sheets are reasonably stable and so on. So these are all characteristics of the Earth system in a fairly well defined fairly stable state, the most recent of which is the Holocene.

Stone: So how would you define the Holocene, and I understand that was about the last 10,000 or so years ago. And that was the period during which humanity, or not humanity, but I guess modern society developed?

Steffen: You know, that’s right. The Holocene is roughly the last 11,700 years. And it’s the most recent of the warm or interglacial periods, after the Earth has come out of an ice age and we humans, fully modern humans, homosapiens, have existed through roughly two of these cycles of long cold ice ages, more erratic climate, and then short intervening warm periods.

So the Holocene has been a pretty important one for humans because it’s been slightly cooler than the three or four that came before it, but it’s longer and more stable. And that’s due to the Earth orbital parameters, its orbit around the sun, its precession, its tilt, and so on. So some complicated maths there, but you can work out why it is, as long as stable as it is.

But these characteristics have been very important for humans because we’ve had a reasonably stable water cycle. In other words, you had reliable rainfall in large areas of the world. This allowed us to develop agriculture. And of course, once we develop agriculture and food surplus, we could develop settlements, we could develop more technologies. And the whole thing, of course, ramps up until you get the modern, highly technologically powerful societies we have today. But it’s all based on the fact that we had nearly 12, we’ve had nearly 12,000, periods stability, which allowed humans to develop agriculture and settle down and develop settlements. And so that was really the key, I think, to why the Holocene is so important for us.

Stone: And it sounds like the shift is actually putting all those conditions in jeopardy. So when exactly did the Anthropocene begin?

Steffen: Well, there’s been a lot of debate on that, but certainly from two very important perspectives, the answer is very clear. That’s a perspective from Earth System Science, where I work, but also from the geological stratigraphic perspective. And by far, the best start date for the Anthropocene is the mid-20th century, somewhere around 1950.

We can see all sorts of changes in the Earth’s system, begin at a very rapid rate at that time. We can see global average surface temperature rising, we can see changes in greenhouse gases in the atmosphere, we can see changes in extinction rates, changes in ocean acidity, all these things. And they all tend to sweep up with dramatically increasing rates at about the mid-20th century.

The second thing we can say is these curves that started then take all of these parameters outside of the Holocene envelope of variability. In other words, we can say for certain that these conditions that started in the mid-20th century, are no longer Holocene like conditions. But the second point we can say really clearly is we know for sure what’s driving that. It’s not natural variability in the Earth system, it’s these direct and indirect pressures from human activities, changing land cover, more use of energy, obviously, a lot of that fossil fuel driven energy, which increases greenhouse gases, which changes the climate, which is changing the water cycle, and so on, and so on. So this is, the bottom line here is from about the mid-20th century, we’ve seen conditions move outside of the Holocene norms. And we know for certain that human activities are the dominant driver of these changes.

Stone: Will, in some of the research I did before we got on the call here, I saw that in the Holocene, the concentration of carbon dioxide in the atmosphere generally ranged from around 270 to 280 parts per million. And then in the middle of the 20th century, it kind of permanently went above that level. So, was that one of the markers that we’ve. one of the markers that you’re going upon here?

Steffen: Yeah, indeed. And that’s obviously an important one. Because when you look at the longer history of the Earth system, you find that carbon dioxide is an extremely important gas in terms of regulating Earth’s climate. And it’s been much higher, and during the ice ages lower, due to natural oscillations in the Earth’s system. And that, of course, has been a good thermostat for the climate when CO2 was very low, as low as 180 parts per million. We’re sitting at a bit over 400 today.

But during the depth of the last ice age, it got as low as 180. And of course, the earth was much colder, with big ice sheets over large parts of North America and Europe, for example. But in in the more distant past, you’ve seen, we’ve seen CO2 concentrations 400, 500 ppm, even 1000 ppm, going further back in time and the Earth was much hotter back then than it is today.

Stone: Going back against you said beginning with the middle of the 20th century, things started to change. I assume more emissions, more economic activity, can you give a little bit more insight into what really cause that the acceleration of change, I guess, from that mid-20th century point?

Steffen: Yeah, that’s a really good point. And, of course, people will immediately talk about technologies. And of course, that’s true. We develop technologies that allow us to mine a lot of minerals, a lot of fossil fuels, to energy technologies, and so on. But really what sits under this, I think, is really the socioeconomic part of the story is that, that leading up to the mid-20th century, we had two world wars, with a great depression in between. And of course, that really retarded any, sort of long-term human development, we were fighting each other and trying to survive.

But what that did was it broke down a lot of earlier feudal institutions that were still around, coming out of the 1800s, and so on. And it finally and emphatically ushered those out and ushered in a new set of institutions, some of which are called the Bretton Woods Institutions, that really grease the wheels of a global economic system and allow that modern phenomenon of globalization, ever increasing consumption, ever increasing connectivity, technological development, that whole thing that we sometimes call the great acceleration in human activity.

So ultimately, according to two social scientists that I talked with, it really was the social, economic, and institutional post World War II developments that are fundamentally are, that fundamentally underlie, the beginning of the Anthropocene.

Stone: Why is the concept of the Anthropocene itself important? Why do we need to mark this change in geologic epochs? Why is that important to us?

Steffen: Well, I think first of all, from the scientific community, it’s important because we Earth system scientists study the Earth system, how it operates, how it changes, what states it can exist in stably, what triggers transition. So for us, this is a really, really interesting phenomenon of one species, becoming so powerful, so fast, that it’s actually shifting the operation state of the Earth system. The geologists are very practical, they have a very simple question they ask, can you see significant globally synchronous signals in the stratigraphic record that show that what’s happening above those signals is significantly different from that below

Stone: Is that the rock layers we’re talking about essentially?

Steffen: Yes, not necessarily rocks, they use a number of possible indicators. They use lake sediment cores, they use ocean, continental basin sediment cores, they can use ice cores, they can use speleothems, they can use pollen records. They can, so a number of archives in the Earth that have traces of how the Earth has behaved and how it’s changed. For example, the beginning of the Holocene 11,700 years ago, is actually an ice core from the Greenland ice sheet that’s kept in a nice lab in Copenhagen, Denmark. But you can see the point at which isotopes of oxygen and hydrogen and carbon dioxide itself stabilized after coming out of the last ice age, that’s a very clear record in that ice core. So that’s the means by which geologists determine the time periods in Earth’s history.

Stone: So if I understand correctly, one of the, kind of the big reasons, this is important as well as that, once the Anthropocene really gets underway, it’ll take on a life of its own, there will be certain thresholds that will be surpassed. And it’ll be kind of a self-sustaining cascade of events that will bring us to a much warmer Earth, that you’ve characterized as hothouse Earth in your writings. And this will be the new normal for our climate and it will be very inhospitable place, at least compared to what we have today. Are we truly on this path to the hothouse Earth now?

Steffen: At the moment we are. And of course, what we have to say here is that this is a hypothesis that a group of us have put forward. We think there’s a lot of evidence for it because it’s very consistent with how the Earth systems behaved in the recent past, where it has oscillated between ice ages and warm periods, with sharp, sharp transitions in between. But the important point is those transitions are not driven primarily by changes in solar radiation or changes in the Earth’s orbit. They only have this triggers. The heavy lifting is done by internal processes in your system, so called feedbacks, like the melting of ice, like the release of carbon from melting permafrost or burning forests and that sort of thing.

So what we’ve done is we’ve actually looked forward and looked at some of these feedback mechanisms that we know exist and know have operated before in the recent past. And put those together in a coherent picture, sort of like a row of dominoes. If you start tipping some of these feedback mechanisms, can you actually push the dominoes, get the dominoes to go over all of them in a tipping cascade, as we call it. And that’s actually how the Earth system behaves, it doesn’t behave as a nice, well behaved linear system.

So our concern here is pretty much as you put it. If we push the Earth system too hard, primarily by pouring more greenhouse gases into the atmosphere, but also by degrading the sinks of carbon, the stores of carbon, the Amazon Basin for example, the northern forests. These things could form a tipping cascade and take the earth to a state that we saw, probably about 15 to 20 million years ago. So that’s in the recent past in Earth history. We know it’s a stable state, it’s four or five degrees hotter, has much less ice, much higher sea levels, and is difficult for large mammals to live in.

So this is the sort of hothouse Earth trajectory we’re talking about. And yes, to answer your question, at the moment, we are on that trajectory. We’re starting to see some of these feedbacks kick in, we don’t think we’ve started the cascade yet. In fact, we’re pretty sure we haven’t. But we see the beginnings of some of these feedback processes. But importantly, we see the human stress intensify. In other words, the rate at which CO2 is rising in the atmosphere is itself increasing. So the rate is increasing. So even though we humans now understand, and have for a couple of decades, the nature of this problem, so far, we’ve proven to be totally incapable of stopping the rise of CO2 in the atmosphere.

Stone: You’ve worked on climate issues on Australia’s Climate Commission, and as the Head of the International Geosphere Biosphere Program, which I believe no longer exists. Has the Anthropocene concept taken on importance in policy circles? I mean, what you’re just telling me is pretty, it’s kind of a scary scenario, does this impact policymakers? What do they make of it?

Steffen: I don’t think it’s impacted policymakers too much yet. I think there’s been a lot of discussion in the popular press, in the popular media, and in various circles on the Anthropocene. And I think that’s a really good thing. It’s a hugely important pretty scary topic that needs to be out there and discussed. I think in the policy circles, in the governmental circles, there’s far more of a focus on climate change as a part of the Anthropocene and indeed an extremely important part of the Anthropocene.

So the issue here is that, certainly up until now, human emissions of greenhouse gases, mainly CO2 are indeed, by far the dominant driver of change. The concern is, if we start passing these tipping points, then these feedbacks intrinsic internal to the system, will also become important and eventually take over, of course, that’s hothouse Earth. So the challenge we face, and of course the challenge that we faced here in Australia when I was on the climate commission was, how do we then take this big problem and distill it down to what we can do, in this time period, in these economies, in these societies, to turn those emission curves down, and get emissions going in the opposite direction. So far, a few countries have been able to do that. But by and large, we have not been successful in doing that.

Stone: You said a minute ago, you talked about climate change as just a part of this larger shift that we’re seeing. And there’s also this concept that you’ve written about of planetary boundaries. And these are changes in the Earth that once you cross them, you either exhaust certain resources that are essential to Earth as we know it, to life in certain ways. Or you get into this kind of domino effect that you talked about earlier, in some of these boundaries, go into areas that don’t really have a whole lot to deal with, directly with climate. We talk about, maybe they do, biochemical flows, ocean acidification, ozone depletion, etc. There are a lot of different factors beyond climate itself that this is all about.

Steffen: Yeah, that’s true. There none of them, in fact, that we have in our planetary boundaries framework. And the idea we had here was this Earth system scientists to say, if you could distill down this huge complex system, which provides our life support system for humans and the rest of life, what are the minimum number of processes you need to define the system? And we distill those down to nine. But they’re not all equal. We have two, and potentially three, what we call core planetary boundaries because they on their own, could push the Earth system into a new state.

One is climate change, for the reasons we’ve just been discussing. The other one is what we call biosphere integrity. That’s the integrity of the biosphere part of the system. And that on its own, if we drove the sixth great extinction event, even if we kept climate stable, that’s just through direct pressure on the biosphere, there would be a new state of the Earth system. But there is a sort of a joker in the pack that we haven’t talked too much about. And there is a third planetary boundary, which could also we think, broadly your system into a new state. And that’s what we call novel entities.

That’s new things that do not exist naturally in your system. But humans are inventing them and throwing them in. You can think of all sorts of things radioactive materials, plastics, aluminum, electromagnetic radiation that we use for mobile technologies, potentially artificial intelligence. These things are all alien to the Earth system. And so they have the potential to disrupt how the Earth system operates. The other six feed into these, these two or three, things like the big elements cycles of phosphorus, nitrogen, and so on. Things like land system change, deforesting the tropical forests, things like freshwater use.

So we’re trying to paint a coherent picture of the Earth system as a whole. But yet, make it practical enough that managers that policymakers can see where the levers might be to manage our own activities to keep the system in a stable state. That’s the whole idea of the planetary boundaries.

Stone: And getting back to geology for just a moment, I assume that at some point in the future all these changes will be will be imprinted in the geological record when somebody looks at the strata from the year 2018, 2019?

Steffen: Yeah, in fact, you can go back now and see it accumulating in the strata, because we do have stratigraphic records that go back, obviously, several centuries, several millennia, and so on. But they come through right to the present. They come through to 2018. And soon to be 2019.

You can already see that, you can see radioactive materials appearing from mid-20th century, you can see plastics appearing from mid-20th century. You can even see an Anthropocene chicken bone from mid-20th century. And that is, when I was a lad growing up in the middle of the U.S. and we had roast chicken and so on the chicken wait a little under a kilogram. And nowadays, the chicken weighs over four kilograms. And that’s actually evident in the bone structure. And so when you look at the bones accumulating in the strata of these chickens, and there are quite a few of them, you can see the bone structure change in the mid-20th century.

So I think this particular has had a wealth of information that’s already there, it’s already accumulating, and they can already see changes from around the mid-20th century. So I think if you go further in time, assuming we humans are still around, you know, 500 to 1000 years from now, who knows what the strata is going to look like. But it will certainly change quite dramatically from the mid-20th century, and probably continue to change for quite some time.

Stone: So we are seeing a shift from getting back to our earlier part of our conversation from the Holocene, which was kind of the ideal conditions, as we understand it, for humanity in which humanity could exist. It seems like going forward, one of the issues that we’re getting out here is that we want to maintain those conditions in the future. But the Earth is spiraling towards this new hotter equilibrium point that it’s going to find at some point in the future.

So let’s talk about the solutions. Are there solutions that can stop that process from happening? In which we can somehow keep the earth a little bit more Holocene-like?

Steffen: Yeah, really good question. Obviously, there has been a lot of work on what needs to be done. We know that emissions need to be reduced. Greenhouse gas emissions deeply and rapidly. We know we’ve got to protect more of the Earth’s surface. We know we’ve got to stop throwing chemicals and plastics, into the Earth system. We know all that stuff.

So a lot of the technical the practical things that need to be done, are known. The problem is to do those requires deep shifts in our governance systems, in our socio-economic systems. And a lot of social scientists that I work with are increasingly saying, and this actually needs to be underpinned by changes in our value systems, changes in our belief systems as to who we are, what are we doing here on planet Earth? What type of future should we leave for our children and indeed for the rest of life on planet Earth.

So it takes you very quickly back from technological solutions like ways of pulling CO2 out of the atmosphere and storing it underground or ways of generating energy without emitting CO2 and all the technical stuff that gets the enormous amount of airplay. All the way back down to really fundamental values. And one thing that comes consistently through is that the person, socio-economic system is very destructive and actually putting us on the path to the Anthropocene and possibly to hothouse.

So there’s an increasing questioning of the of the post World War II socio-economic, particularly economic system that we’ve developed and how that needs to be transformed. And to do the transformation, we need and underlying shift in value systems and so on. So it’s a really rich discourse that’s going on now, much more broadly, then the physical science community or the technological community to philosophy, to history, to culture, and so on. So it’s an interesting time.

Stone: This really isn’t then just a geologic shift, or a technological cause, we’re really looking at a whole societal, socio-economic driver for this, right. You know, I’ve seen the Anthropocene renamed as that, if I pronounced this correctly, Capitaloscene. You know, the capitalism era, it’s more reflection of what our economic systems have driven us to value consumption, for example, with these with these impacts.

Steffen: Yeah, that’s right. And that’s, that’s a very good point. That I think this discussion really is starting to emerge quite strongly. But I think laying behind this is we need to look at ourselves as a species. And what we’ve built as a complex system, that now is, the reason to be is important as the geosphere and the biosphere in terms of the Earth system. We’re still part of the Earth system, of course. And that’s what a lot of people tend to forget that out there somewhere with the Earth as a climate, actually, we’re part of it.

And you could argue that through Earth’s history, really, from about 3.5 to 4 point billion years ago, most of it, it’s been the geosphere and the biosphere that’s co-evolved. And they’ve co-evolved through various stages. And some scientists are saying that the anthroposphere, us, is the third major partner of the Earth system. And it’s becoming so powerful, that it’s driving the third distinct period in the history of the biosphere.

First being simple bacteria, single cell organisms, which are around for a long time. Then came complex animals, the metazoans. But the third stage of biosphere evolution may in fact, be human directed evolution through a variety of reasons. So there are some discussions out there, they’re really quite profound in terms of the impact of humans, whether you call it Capitaloscene, or Anthropocene, or whatever, of our human society is on the entire evolutionary future of the of the Earth system, both in terms of its climate and biosphere.

Stone: So can we maintain that state that we need to be in? That kind of artificial Holocene?

Steffen: Well, that’s the question we face now over the next couple of decades. And I think the decision points coming up very soon. So we call it in our analysis, we call it stabilized earth. Because it’s not really a naturally stable part of the state of the Earth system. So in other words, we can’t just meet the Paris two degree target, park the Earth system at two degrees, and expect it to stay there. It probably won’t because of intrinsic feedback.

So we’re going to have to become stewards of the Earth system, intelligent stewards of the Earth system, to maintain it in what some might call a super Holocene state, or a super integrational state. Something that’s hotter than the Holocene, but certainly not as bad as hothouse Earth. And one that hopefully will be able to survive and perhaps even thrive in.

So that’s the goal. That’s the target we’ve got to do. Now, we’ve lost the Holocene. We’re not going to go back to it for a number of reasons. But we’ve got to say, we can’t let ourselves sleepwalk into a hothouse Earth state. We actually have to wake up and say, given that we are now the dominant driver of change in the Earth system, we have to think really carefully about what that means and where we’re going.

Stone: Let me ask you a final question here, if I may. It does look like there will be need for some sort of global governance, capable of managing the Earth’s climate as a whole. Do you see that need in could climate be the issue, in essence, that gives rise to some form of global government with teeth?

Steffen: Yeah, look, that’s the critical question. I think we need to distinguish two words, two concepts. One is government, as we all know, but there was governance, which is a much broader, more encompassing concept. That simply means, how do we organize ourselves to achieve objectives we want to achieve? It doesn’t mean that there would be a single global government.

There is an attempt today at global governance. It’s called the United Nations. And it hasn’t worked very well. But that’s an attempt where you still keep your nation state sovereignty, but you work together to manage yourself in the context of the whole planet. So obviously, we really need to think about what sort of governance systems do we need at the planetary scale? Now that it’s absolutely clear that Homosapiens is a key driver of the future of the planet.

So we simply can’t avoid this question. And to me, the critical question is, how do we reconcile what we need to do to stabilize the Earth system with the concept of national sovereignty? Which of course is a couple of centuries old the Westphalian concept? Or do we need to radically change the concept of sovereignty, national sovereignty? Those are questions that really need to be taken head on and discussed very seriously and very carefully.

Stone: Will, thank you very much for talking.

Steffen: My pleasure, Andy.

Stone: We’ve been talking with Will Steffen, emeritus professor at Australian National University, about the new geologic epoch known as the Anthropocene. For more insights into climate and energy policy, check out the research section of the Kleinman Center for Energy Policy website. Our web address is kleinmanenergy.upenn.edu. And our Twitter handle is @kleinmanenergy. Thank you for listening to Energy Policy Now and have a great day.


Will Steffen

Emeritus Professor, Australian National University
Will Steffen is the former executive director of the International Geosphere-Biosphere Programme, and a former member of the Australian government’s Climate Commission.

Andy Stone

Energy Policy Now Host and Producer
Andy Stone is producer and host of Energy Policy Now, the Kleinman Center’s podcast series. He previously worked in business planning with PJM Interconnection and was a senior energy reporter at Forbes Magazine.